ESG White Paper Dell Equal Logic Optimizing Server Virtualization May 2010

8/2/2019 ESG White Paper Dell Equal Logic Optimizing Server Virtualization May 2010

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WhitePaper

Optimizing Storage for Server Virtualization

Why an Enterprise-Class Fully-Virtualized iSCSI SAN is more Cost Effective

than Legacy NAS, SAN and DAS in Virtual Server Environments

By Brian Garrett and Mark Bowker

May, 2010

This ESG White Paper was commissioned by Dell EqualLogic, Inc.

and is distributed under license from ESG.

2010, Enterprise Strategy Group, Inc. All Rights Reserved


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White Paper: Optimizing Server Virtualization with Cost-Effective, Enterprise-Class Storage 3

2010, Enterprise Strategy Group, Inc. All Rights Reserved.

Introduction

Server virtualization and consolidation technologies can help organizations struggling with cost containment and

continuing information growth. Many have already implemented server virtualization, while others are planning to

either start or accelerate virtualization deployments. The reduction in hardware costs is certainly attractive as

increased resource utilization and physical serve consolidation keep total cost of ownership (TCO) down.

ESGs annual spending survey indicates that key IT priorities for the next 18 months include an increase in servervirtualization deployments (see Figure 1). Of 515 surveyed users, 33% selected this as their top priority. Improving

data backup and recovery was third, with 27%this remains a perennial favorite as protecting information seems

to always be on the minds of IT professionals.1

Figure 1. Top 10 IT Priorities Over the Next 12-18 Months

Source: Enterprise Strategy Group, 2010.

Storage Choices

One challenge with deploying server virtualization is selecting the right storage infrastructure that will serve as a

foundation and scale to meet the challenge of top tier applications. Direct-attached storage (DAS), networked-

attached storage (NAS,) and both Fibre Channel (FC) and iSCSI storage area networks (SANs) are viable for servervirtualization; however, they are not equal in terms of functionality, ease-of-use, or cost.

Direct-attached storage is the term used to define the hard drives inside of, or directly attached to, a

server; capacity can be attached using SCSI, SATA, or SAS connections. In contrast, FC SANs, multi-protocol

NAS, and iSCSI SANs are connected to servers through a shared storage network.

FC SANs provide block-based storage. They connect to servers using FC HBAs on the hosts and FC switches

in the network and are traditionally built as modular, dual-controller systems.

1Source: ESG Research Report, 2010 IT Spending Intentions Survey, January 2010.

19%

20%

21%

23%

24%

25%

27%

27%

28%

33%

0% 10% 20% 30% 40%

Regulatory compliance initiatives

Large-scale desktop/laptop PC refresh

Business continuity/disaster recovery programs

Data center consolidation

Major application deployments or upgrades

Manage data growth

Upgrade network infrastructure

Improve data backup and recovery

Information security initiatives

Increase use of server virtualization

What are your organizations most important IT priorities over the next 12-18

months? (Percent of respondents, N=515, ten responses accepted)


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NAS deployments offer file-based storage and connect hosts to storage arrays using an Ethernet LAN,

standard Ethernet adapters and switches, and the NFS and CIFS file serving protocols.

iSCSI SANs offer block-based storage and use the iSCSI protocol over Ethernet along with Ethernet NICs and

switches.

These server virtualization storage alternatives are shown in Figure 2. In the DAS deployment, storage resources

are not shared; each array is attached only to a single server. SAN and NAS implementations share storage over a

network. In recent years, storage vendors have been producing unified storage arrays that offer multiple protocols

in a single array; for example, most legacy NAS solutions have evolved to support iSCSI. Unified solutions that have

evolved from a legacy NAS heritage typically implement the iSCSI protocol as an additional protocol layer which is

used to access data that is ultimately stored in a file system hidden inside the storage.

Figure 2. Virtual Server Storage Deployment Options


iSCSI and Server Virtualization on the Rise

ESG research has noted an uptick in the adoption of iSCSI SANs and server virtualization. As Figure 3 demonstrates,

there has been a significant increase in iSCSI adoption in both midmarket and enterprise organizations. In 2009, ESGsurveyed 1,433 North America-based storage and IT professionals. Overall, 28% of respondents had adopted iSCSI,

compared with 18% in 2006. In addition, ESGs research indicates that 24% of respondents plan to use iSCSI SAN

technology in the futureleaving less than half (48%) with no iSCSI implemented or planned. iSCSI is definitely

mainstream, and growing.2

2Source: ESG Research Brief, iSCSI SAN Adoption Update, January 2010.


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Figure 3. 2006 vs. 2009 iSCSI SAN Adoption, by Midmarket vs. Enterprise


Why the increase? Widespread market acceptance of any technology usually only occurs when that technology has

both broad capabilities and applicability. The basic value proposition of course must be sound, but broad and

increasing adoption signifies a product that can play in multiple markets and segments. iSCSI storage has reached

this level and is now commonly found in both midmarket and enterprise organizations supporting not just test and

development, but Tier 1 applications.3

Server virtualization deployments are also on the rise according to ESG research conducted in March 2009. In 54%

of the enterprise and 32% of the midmarket segments, server virtualization was already in use in production

environments. Only in 24% of both groups was virtualization used solely in test environments. Also, 44% of

midmarket organizations had not deployed virtualization, while only 23% of enterprise organizations had not yet

done so.4

The adoption of iSCSI is tightly correlated with the emergence of server virtualization as a common infrastructure

deployment. In a fall 2009 survey, 55% of iSCSI users said they had deployed iSCSI specificallyto support server

virtualization projects. Server virtualization has helped to move more storage off of DAS and onto the network

with Ethernet being so ubiquitous, iSCSI is a logical choice, particularly for block-based applications such as e-mail

and databases. Not surprisingly, the top three reasons that users deployed iSCSI SANs were storage consolidation,

cost reduction, and server virtualizationall rooted in reducing expenses and improving efficiency.5

The adoption of iSCSI is also being driven by the accelerating adoption of 10 Gigabit Ethernet. An iSCSI storage

system accessed over a 10GbE interface has more bandwidth than a system accessed over 8 Gbps Fibre Channel

interface. This boost in bandwidth is ideally suited for throughput intensive storage applications including data

warehouses, decision support systems and backups. Ethernet can also have a price advantage over Fibre Channel.

Virtualization and data center consolidation have led to top-of-rack and aggregation switches in the data center,

3Ibid.

4Source: ESG Research Brief, Reference Research: x86 Server Virtualization Adoption by Company Size and Number of Servers, March 2009.

5Source: ESG Research Brief, iSCSI SAN Adoption Update, January 2010.

17%18% 18%

25%

29%28%

0%

5%

10%

15%

20%

25%

30%

35%

Midmarket (100 to 999 employees) Enterprise (1,000 employees or more) All respondents

2006 vs. 2009 iSCSI SAN adoption, by midmarket vs. enterprise. (Percent of

respondents)

2006 (N=432) 2009 (N=1,433)


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while increasing network traffic and latency-sensitive content (e.g., video, voice) has driven 10GbE core network

switch sales. As a result, the average price-per-port metric has fallen below the psychologically important $1,000

threshold. These trends will continue for the foreseeable future as 48% of respondents to an ESG survey reported

that they plan on deploying 10 Gbps Ethernet to connect servers to networked storage system over the next 24

months.6

ESG Lab: The Voice of Experience

The analysis presented in the balance of this paper is based on ESGs research and hands-on testing by ESG Lab. Our

analysts have decades of storage and server virtualization experience, including product development, testing, and

real-world application deployment. ESG Lab has tested dozens of storage systems in virtual server environments,

including DAS, SAN, NAS, and iSCSI solutions.

In particular, ESG has been acquainted with EqualLogic since it was founded in 2001 and has tested its arrays

several times since 2003. Most recently, ESG Lab completed hands-on testing and TCO analysis of Dell EqualLogic

solutions in July 2009.7

Dell EqualLogic PS Series iSCSI SAN Solutions

From its inception in 2001, EqualLogic set out with a mission to create simple, affordable SANs; SANs that just

happened to use iSCSI to connect to servers. Much has happened since thenincluding the ratification of the iSCSI

specification in 2004, improvements in network performance, and Dells acquisition of the companybut

EqualLogic has never strayed from its mission. Many generations of arrays and functionality enhancements later,

Dell EqualLogic PS Series SANs have stayed true to their roots: they are simple, affordable, enterprise-class SANs. A

distinct differentiator, however, is the inclusion of all-software functionality in every array at no additional charge.

This is a tremendous benefit as it simplifies management, helps to maintain feature adoption momentum, and

reduces TCO.

At a high level, Dell EqualLogic iSCSI arrays fundamentally change the way organizations purchase and manage

storage. They are built on a patented peer storage architecture that enables components to work together to share

resources, evenly distribute loads, and collaborate to optimize performance and protect data.

The PS Series offers enterprise-class performance and reliability, intelligent automation, and seamless virtualizationof storage for simplified management. Fault-tolerant hardware includes fully hot-swappable, redundant

components and five 9s availability; intelligent automation dramatically simplifies management tasks. SSD, SAS, and

SATA disk drives are supported as well as multiple RAID types for optimizing capacity and performance. Dell

EqualLogic arrays offer all the benefits of storage consolidation (such as better utilization, lower costs, and simpler

management) as well as a modular growth path and automatic load balancing across all resourcesnot just disk,

but also connectivity, cache and controllers. This intelligent storage array offers rapid installation, simple

management, and seamless linear expansion. The flexibility and storage virtualization built into PS Series arrays

allows them to operate effectively in virtual server environments where data movement and flexible connectivity

are essential.

Just as server virtualization can pool server assets and allow for non-disruptive changes to the assets, EqualLogic

storage provides similar decoupling of the logical storage service from the physical hardware. Data can be movedto different hardware while preserving the associated hardware-based snapshot and replication relationships in the

storage. Storage assets can be removed from a pool without downtime and without degrading redundancy,

performance, or snapshot and replication protection. A Dell EqualLogic PS Series iSCSI SAN fully virtualizes storage

across drives, controllers and networks and thus brings the same benefits to storage that VMware brings to servers.

6Source: ESG 2008 Enterprise Storage Systems Survey, November 2008

7See: ESG Lab Report, Dell EqualLogic TCO Analysis, July 2009.


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complicated management and comes with a high price tag. Dell EqualLogic arrays have integrated virtual server

snapshot management capability that enables administrators to ensure virtual machine data protection while

simplifying administration, enabling automatic scheduling, and keeping costs down.

EqualLogic arrays come with Auto-Snapshot Manager/VMware Edition (ASM/VE) and Auto-Snapshot

Manager/Microsoft Editionagain, at no additional cost, of course. These tools are designed to simply create and

centrally manage online, point-in-time copies of virtual machines and data stores using PS Series SAN-based

snapshots. ASM/VE understands the relationships and locations of virtual machines, VMFS Datastores, and PSSeries SAN volumes; the easy-to-use GUI coordinates the creation, recovery, and scheduling of virtual machine

snapshots with vCenter and VMwares native snapshot technology. API-based integration with vCenter delivers

VMFS-consistent snapshots and VM-aware replication. ASM/VE improves the protection, storage utilization, and

performance of VMware-based virtual infrastructures.

Auto-Snapshot Manger/Microsoft Edition software from Dell provides the integration between Microsoft VSS and

the Dell EqualLogic series of storage arrays. ESG Lab has worked with this valuable utility in the lab. As shown in

Figure 5, Auto-snapshot Manager/Microsoft Edition provides a simple, wizard-driven interface which can be used to

create a snapshot, clone, or a replica of applications running in a virtual server environment. The same user

interface can be used to quickly recover an application or an entire Hyper-V virtual machine.

Figure 5. Auto-Snapshot Manager / Microsoft Edition


The Auto-Snapshot Manager/Microsoft Edition allows administrators to safely take snapshots of, backup, and

restore Microsoft applications (including Hyper-V virtual machines) with third-party backup software modules by

supporting VSS and VDS interfaces. It can run the database integrity checking tools proactively on the snapshots to

detect database problems early and to have the integrity checking already done ahead of time. It allows application

administrators to perform recoveries using snapshots, leveraging instant restore of the production volumes when

appropriate, without needing to know the details of the storage layout. It eliminates the extensive configuration

and scripting that other systems require when executing snapshot-based backups.


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The Case for Networked Storage

While DAS is technically an alternative for virtualized server environments, its not a good option. Server

virtualization enables consolidation and improved utilization, which reduces costs. With DAS, the inability to

consolidate and share storage keeps utilization low, which dramatically increases total cost of ownership. More to

the point, you need networked storage to take full advantage of the benefits of virtualization such as better

flexibility, availability, performance, and mobility. With DAS, storage capacity is held captive within or behind

individual servers. Capacity cannot be moved to another server without downtime and disruption. Also, networked

storage is required to take advantage of the valuable disaster recovery capabilities available from server

virtualization vendors (e.g., VMware Site Recovery Manager).

Virtual server technology deployed with networked storage provides a number of significant benefits when

compared to DAS. The numbers of servers and direct-attached hard drives are reduced, as are space, power, and

cooling requirements. Increased server and storage utilization reduces capital equipment costs. Virtual machine

mobility and shared storage pools enhance availability and serviceability. Finally, managing servers and storage

from a single user interface reduces operational costs.

With DAS out of the picture, you must choose an interface for storage networking. Fibre Channel and Ethernet are

currently the two most viable alternatives. Fibre Channel requires not only specific storage networking hardware,

but a significant investment in administrator training to operate due to complexity. Initial performance concernsabout Ethernet-based storage networks have been dismissed, while Ethernet is more ubiquitous and leverages

existing skill sets and hardware.

If Ethernet is the chosen interface, the next step is choosing between NFS or iSCSI as the protocol used for storage

in the virtual server environment. An important consideration is that most organizations will need a block-based

protocol for applications such as e-mail and databases, making iSCSI attractive. Organizations that dont already use

a file-based protocol dont need to deploy one for server virtualization, but those already using NAS can leverage it

for storage networking.

Thousands of customers are using NFS and iSCSI protocols in virtualized environments and ESG Labs experience has

proven that both are viable. The important decisions are around the entire storage systems features and

capabilities, not which protocol to use for the storage network.

Legacy NAS ConsiderationsImplementing NAS for virtual server images may seem attractive at first, but often adds complexity and cost to the

environment. VMware support for virtual server images accessed using the NFS protocol is a good case in point.

VMware virtual server images (i.e., vmdk files) accessed over the NFS protocol can be managed and optimized by

the storage system (e.g. snapshots can be used for quick recovery). Additional advanced storage functions

including remote mirroring and deduplication can be applied to virtual server images for additional value. This

seems attractive until you realize that similar value can be derived using a full features disk array that accesses

vmdk files over a SAN. As a matter of fact, recent vStorage enhancements in VMware allow VM-level copy,

rollback, locking and remote replication while still leveraging the native VMware file system on top of SAN. Dell

EqualLogic has a rich and growing suite of integrated advanced storage capabilities (e.g. snapshots and remotereplication) that work with VMware APIsand dont require the use of the NFS protocol. It should be noted that

much of the data in a VMware virtual server environment is not stored in vmdk files. A vmdk file is typically used

to store the operating system and application executable files (e.g. the C: drive in a Windows server environment).

Application data, including e-mail and databases, is typically stored on another logical drive using a block protocol

(e.g. iSCSI).

In the past decade, dual-controller, modular systems have become the gold standard for NAS, particularly in the

midmarket. Most of these solutions have evolved to support iSCSI and sometimes other protocols as well. While

this multi-protocol support offers the benefit of serving both block and file storage, some vendors charge license

fees for any protocol after the initial one, such as adding iSCSI to a NAS system. In terms of complexity, many


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organizations already use block-based protocols for e-mail and databases because file-based NAS protocols are not

standard for these applications and are often not supported. Think of it this way: if you already have iSCSI for e-mail

and databases, you can add server virtualization to it, but if you deploy NAS for server virtualization, youll probably

need to add more protocols for your e-mail and database applications.

Complexity vs. Ease of Use

In ESG Labs experience, a Dell EqualLogic iSCSI SAN offers industry-leading ease-of-use when compared to legacymulti-protocol NAS and SAN arrays. ESGs July 2009 TCO analysis compared Dell EqualLogic PS Series iSCSI SANs

leveraging DAS, FC SAN, and multi-protocol NAS arrays. On each of the four system types, ESG Lab measured the

number of mouse clicks and time required to perform typical storage management tasks such as configuring a

system from scratch; moving arrays and storage capacity between storage pools; accessing virtual machine

volumes; and performing copy, replication, and recovery tasks. In that report, it was noted that, Every step of the

way, ESG Lab was impressed with how fast and easy it was to manage a growing pool of EqualLogic storage from a

single, intuitive user interface.8

A complicating factor faced by NAS and FC SAN deployments is managing software licensing. Storage array

management, replication/snapshot functionality, host-based snapshot management, hypervisor integration,

performance analysis, and the like all require individual software licenses that must be managed for each array.

Time-consuming and complicated license management is an enormous headache for IT. With the PS Series, allsoftware functionality is included so there are no licenses to track or manage.

Upgrades and scalability are also complications with NAS (and FC SAN) arrays. Traditional dual-controller, multi-

protocol NAS (and FC SAN) arrays must be sized to meet present and future capacity and performance

requirements. They often require controller upgrades along with software and maintenance charges to meet an

organizations needs for application responsiveness as controllers often reach their performance limits before their

capacity limits. In comparison, EqualLogic arrays offer a virtualized scale out approach in which individual arrays can

be added to a shared storage pool non-disruptively to meet ongoing capacity and performance needs dynamically.

This pay-as-you-grow model is much less costly and far easier to use than traditional dual controller arrays.

Internal file system and protocol overhead can lead to performance issue with traditional NAS arrays. EqualLogic

provides advanced block storage functions which are not dependent on an underlying file system inside thestorage. Native block format inside the storage can make for more consistent performance, especially for database

and e-mail applications with sensitive performance requirements and lots of daily updates.

In addition, as capacity is introduced (disks or arrays) to a PS Series SAN, that capacity is automatically added to the

shared storage pool and rebalanced across all available resources. As a result, disk drives, controllers, ports, cache,

and performance scale linearly with an organizations growth. Simple, non-disruptive growth that virtualizes

storage over a pool of controllers and scales in a linear fashion is a key benefit of Dell EqualLogic arrays especially

when compared to legacy NAS systems which support only a pair of controllers.

Cost

As mentioned previously, ESG Lab analyzed the total cost of ownership over five years for multi-protocol NAS, FC

SAN, EqualLogic iSCSI SAN, and DAS deployments. Analysis was based on a theoretical customer requiringapproximately 80 TB of block-based storage capacity to support common business applications. Acquisition costs

for hardware, software, and connectivity; maintenance costs for hardware and software; and the costs of power

and cooling over five years were consideredin addition, the cost of management was analyzed based on hands-on

testing and conversations with EqualLogic customers. The solutions were configured with three disk tiers and

similar functionality (additional configuration details can be found in the report).9

8Source: ESG Lab Report, Dell EqualLogic TCO Analysis, July 2009.

9See: ESG Lab Report, Dell EqualLogic TCO Analysis, July 2009.


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As shown in Figure 6, the TCO of the NAS system is significantly higher than the Dell EqualLogic iSCSI SAN. In ESG

Labs analysis, every cost area except connectivity was more expensive in the NAS system, while power and cooling

costs were very similar for these two configurations. Overall, the multi-protocol NAS solution costs 167% more.

Figure 6. TCO Comparison: NAS and Dell EqualLogic iSCSI SAN


From the start, hardware acquisition costs are higher for the NAS system. Each storage technology was configured

to support remote replication for disaster recovery in the multi-protocol NAS (and FC SAN) solutions. This required

the addition of a second pair of storage controllers and disk drives at the remote site as well as a pair of remote

replication software licenses. In contrast, remote replication is built into the EqualLogic solutions array at no

additional charge. Since individual EqualLogic arrays have their own controllers, they can be deployed locally or

remotely without additional investment in replication software licensing.

The costs of purchasing and maintaining software are key differentiators for EqualLogic. Storage management and

data protection services are included with each PS Series array, while NAS solutions tend to incur additional charges

for advanced management and data protection. As shown, software cost is nonexistent on the EqualLogic side of

the chart. Maintenance costs are also much higher on the NAS sidein part because with the PS Series, no software

maintenance charges are incurred.

In terms of management, ESG Lab calculated the time and effort required to complete numerous tasks on each

system. Tasks included monitoring, planning, provisioning, expanding, setting up and recovering snapshots, setting

up and testing disaster recovery, and configuring storage tiers. ESG Lab calculated the number of hours required to

manage each solution over five years and then calculated the cost of paying a storage administrator based on thehours required. All told, managing the NAS Solution over five years would cost about $187,000, while managing the

Dell EqualLogic solution costs about $105,000.

In summary, the five-year TCO of a multi-protocol NAS system is 2.5 times higher than the TCO for the Dell

EqualLogic solution. ESG hands-on testing and analysis indicates that PS Series arrays are easier to manage, work

well in virtual server environments and cost less.


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Legacy SAN Considerations

Complexity vs. Ease of Use

When comparing the FC SAN with a Dell EqualLogic iSCSI SAN, the principle remains that the arrays features,

usability, and affordability matter more than the protocol. However, in the case of Fibre Channel, the storage

network is by definition more complex and costly: it requires specific HBAs on the hosts and SAN switches in the

storage network. Administrators must configure SAN zones, assign LUNs, and configure access control. Ensuringthat arrays have the proper HBA drivers adds yet another level of complexity.

Like legacy NAS system, legacy modular FC SAN systems tend to be more complicated when it comes to upgrades

and scalability. Upgrades often require additional controllers to meet performance and capacity needs as well as

disaster recovery implementations. Legacy FC SANs often have less complete virtualization of RAID and disks inside

the storage, which can require careful planning that would not be required in a more virtualized solution.

Our TCO analysis indicates that legacy SAN solutions are harder to manage than PS Series SANs. In fact, ESGs

analysis indicates that a legacy FC SAN takes more than twice the manpower to manage as a Dell EqualLogic iSCSI

solution. Additional time and effort are required to wire, zone, and configure access control after the SAN changes

as well.10

Cost

Key factors in FC SAN deployments are the cost of Fibre Channel switches and HBAs for every host. These add

significantly to acquisition and ongoing maintenance expenses. As shown in Figure 7, the cost differential between

the FC SAN and the Dell EqualLogic SAN over five years is significant. For the entire cost of a PS Series SAN, you

could purchase only the hardware for a FC SAN without any advanced software functionality. Power and cooling

costs are similar, but connectivity and maintenance are much more expensive on the FC side. Finally, the

complexity of managing the FC infrastructure makes it more than twice as expensive as a simple, intuitive Dell

EqualLogic system. Overall, our analysis indicates that the five-year TCO for a Fibre Channel SAN is three times that

of a similarly deployed Dell EqualLogic iSCSI SAN.

Figure 7. TCO Comparison: FC SAN and Dell EqualLogic iSCSI SAN


10Source: ESG Lab Report, Dell EqualLogic TCO Analysis, July 2009.


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The Bigger Truth

ESGs 2010 IT spending intentions survey indicates that increasing server virtualization and improving data

protection top the list of IT priorities. With these priorities in mind, care should be taken when choosing which

storage system will support a growing virtual server environment. Direct attached storage is inflexible, inefficient,

and complex to manage in growing virtual server environments. For the utmost in flexibility and availability,

networked storage is clearly the way to go.

ESGs analysis indicates that the storage networking protocol chosen for a virtual server environment is of little

importance. What matters more is whether the storage solution is cost effective and easy to manage. Advanced

functionality is important as well. In virtual server environments, it is important that the storage infrastructure

provide not just basic storage and retrieval, but complete data protection including the ability to roll back in time

and recover easily. As server and application administrators are increasingly being asked to handle storage and

virtual server environments, automation and ease of use matter more than ever.

Dell EqualLogic PS Series iSCSI SAN solutions are ideally suited to meet the storage needs in a growing virtual server

environment. With a clustered architecture that leverages industry standard server and Ethernet technologies, a PS

Series SAN bring the benefits of server virtualization to the storage domain as it fully virtualizes storage across

drives, controllers and networks.

ESG Labs five-year TCO analysis indicates that acquisition costs for multi-protocol NAS and FC SAN solutions are

more than twice those of a comparably equipped Dell EqualLogic system (217% and 272%, respectively).

EqualLogics iSCSI approach and disruptive pricing model, including valuable storage software at no additional

charge, are key to those differences. ESGs analysis indicates that a multi-protocol NAS system is 2.5x the TCO for

EqualLogic, FC SAN is 3X, and DAS is 1.4x.

Figure 8. The Dell EqualLogic Cost Advantage


Based on this evaluation, ESG believes that the Dell EqualLogic PS Series offers a distinct advantage for virtual

server environments. As Figure 8 demonstrates, DAS may initially cost less for small virtual server deployments, but

it lacks flexibility and high availability. Cost and complexity will increase exponentially as the number of virtual

machines grows. At some point, managing many islands of storage makes the solution cost prohibitive. Networked


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modular Fibre Channel and NAS solutions reduce costs as the number of virtual machines increases, but the need to

add new dual controllers to accommodate growth increases cost and complexity in steps. In contrast, our analysis

has proven that the Dell EqualLogic iSCSI SANs offer the lowest TCO. Dell EqualLogic PS Series arrays are easy to

use and affordable, avoid the step increases in cost and complexity, and are less than half the cost of NAS for the 75

TB solution analyzed by ESG. Last, but not least, note that as the number of virtual machines continues to grow,

Dell EqualLogic widens the gap and accelerates the savings with on-demand expansion and easy management.

While its been shown that iSCSI, Fibre Channel, and NAS systems are all viable options in a virtual serverenvironment, it should be noted that iSCSI is quickly becoming the interface of choice. ESG recently asked 318

North America-based IT professionals within enterprise and midmarket organizations which storage technologies

they currently use to support their virtual sever environment: 73% reported using iSCSI compared to 52% for FC,

38% for DAS, and 37% for NAS.11

From ESGs perspective, the message is clear. If you are considering a storage solution for your virtual server

environment, do your own analysis. Be aware that some vendors are pushing NAS for virtual server environments

and touting its benefits: consolidating and sharing storage; higher utilization and lower cost; and the flexibility,

mobility, and performance to take full advantage of server virtualization. Be cognizant of the fact that those

benefits are the same for any networked storage solution. NAS is not necessary for server virtualizationiSCSI,

Fibre Channel, and NAS will all work and even DAS is possible. And since most organizations need block-based

storage for other applications anyway, NAS on its own may not be able to meet all of your storage needs in a virtualserver environment. An iSCSI or FC SAN may be needed as well.

Dont get hung up on the particular protocol or featureconsider the whole storage solution and then schedule an

evaluation of the Dell EqualLogic PS Series. Youll be glad you did.

11Source: ESG Research Report, iSCSI SAN Usage in Virtual Server Environments, December 2009.


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ESG White Paper Dell Equal Logic Optimizing Server Virtualization May 2010

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